/* eslint-disable prefer-exponentiation-operator */
/* eslint-disable unicorn/no-zero-fractions */
// 假设 perm 数组已经定义，这里需要声明其类型
const perm: number[] = [
  151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140,
  36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120, 234,
  75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33, 88, 237,
  149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48,
  27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105,
  92, 41, 55, 46, 245, 40, 244, 102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73,
  209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 135, 130, 116, 188, 159, 86,
  164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123, 5, 202, 38,
  147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189,
  28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101,
  155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232,
  178, 185, 112, 104, 218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12,
  191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31,
  181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
  138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215,
  61, 156, 180,
];

function perlin(x: number): number {
  // 整数x1和x2的坐标
  const x1: number = Math.floor(x);
  const x2: number = x1 + 1;

  // x1和x2的梯度值
  const grad1: number = perm[x1 % 255] * 2.0 - 255.0;
  const grad2: number = perm[x2 % 255] * 2.0 - 255.0;

  // x1和x2指向x的方向向量
  const vec1: number = x - x1;
  const vec2: number = x - x2; // 修正了变量名（原代码中是 vec3）

  // x到x1的距离即vec1，利用公式3计算平滑参数
  const t: number = 3 * Math.pow(vec1, 2) - 2 * Math.pow(vec1, 3);

  // 梯度值与方向向量的乘积
  const product1: number = grad1 * vec1;
  const product2: number = grad2 * vec2; // 修正了变量名（原代码中使用未定义的 vec2）

  // 插值
  return product1 + t * (product2 - product1);
}

if (import.meta.main) {
  console.log(perlin(0.5));
}
